This application is a continuation of U.S. patent application No. 10/263,352, filed Oct. 3, 2002.
This application claims the priority of German Patent Application No. 101 48 931.5 filed Oct. 4, 2001 which is incorporated herein by reference.
The invention relates to an espresso machine having a rotating ceramic disk valve as a selective water/steam distributor. More specifically, the present invention relates to an espresso machine having a rotating ceramic disk valve as a selective water-steam distributor that is in a driving connection with a drive motor, and a control device for controlling the drive motor.
Known espresso machines are typically designed not only for preparing espresso, but also milk froth for cappuccino or hot water for various uses. For this purpose, these espresso machines have manually- or program-controlled valves that connect a hot-water generator or a steam generator to the respective functional element, such as a nozzle for discharging hot water. Instead of comprising an arrangement of magnetically controlled individual valves, more modern machines are preferably equipped with rotating ceramic disk valves and formed as multi-directional valves. Such valves can connect a selected discharge line of, for example, a hot-water generator or a steam generator, to a line supplying a functional element, such as a nozzle, depending on the rotational-angle position. The ceramic disk valves essentially comprise a stationary ceramic disk having flow-through openings, to which the supply and discharge lines of the liquid or gaseous medium to be controlled are permanently connected; a second rotating ceramic disk, which is concentric relative to the stationary ceramic disk and rests, spring-loaded, tightly against the first disk; and connecting conduits. The second rotating ceramic disk, when in certain rotational-angle positions, connects the selected supply- and discharge-line openings to one another. A drive motor that serves to set the ceramic disk valve can be controlled either manually or, in automatic operation, by a program switch mechanism, i.e., a control device.
In one known espresso machine, which has a rotating ceramic disk valve as its selective water distributor, but is otherwise of the generic type mentioned at the outset, a driving pinion keeps an electric drive motor in direct gear engagement with a serrated disk that is connected to the rotating ceramic disk of the disk valve (EP 1 106 126 A1). To attain a very high precision in setting the angle of rotation of the rotating ceramic disk, a stepping motor can be provided as the drive motor. The control of the stepping motor, which requires a number of individual pulses for adjusting the disk valve, may be very complicated and may not produce the desired result, for example, because the stepping motor does not follow all of the pulses of the controlled operating voltage during the startup procedure, and/or is slow during the shutoff process because of the moment of inertia of the disk valve connected to it and the gear elements. The latter disadvantage is even more prevalent in simpler drive motors, for example, in a synchronous motor or a universal motor in place of the stepping motor, even if the drive motor is switched off, cam-controlled, in a desired rotational position of the rotating ceramic disk.
Attaining an exact rotational-angle position of the rotating ceramic disk of the disk valve, and thus a fast, exact alignment of the openings in the disk valve that are to be connected to one another, is usually desirable for assuring reliably uniform flow quantities and avoiding interfering flow noises, which may occur at hole edges if the openings are not perfectly aligned.
It is therefore the object of the present invention to provide an espresso machine having a rotating ceramic disk valve as a selective water/steam distributor, such that the precision of the adjustment of the rotational angle of the disk valve is improved in a simple manner.